shadowsocks / shadowsocks/shadowsocks-org

server and client should not share the same subkey

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#153 3 comments 0 reactions 0 assignees View on GitHub

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Description

As client and server share the same key the same info string "ss-subinfo", secret messages of aes-gcm might be encrypted by the same key if random salt is same.

Due to random salt is visible, if some one could store several peices of communication message and wait for the time when client and server have used the same random salt. It could get some useful information from secret message.

For detailed information, please check Nonce-Disrespecting Adversaries: Practical Forgery Attacks on GCM in TLS (camera-ready version / Usenix WOOT16).

All in all, make nonce unique. Subkey should be different between client and server.

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First steps

  1. Read the whole issue, then the project's contributing guide.
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  3. Fork the repository and make your change on a branch.
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Research direction

The issue names no files, tests, or implementation entry points. Start by locating the protocol code that derives the client and server subkeys, then verify that the two directions cannot reuse the same key or nonce; done means the directional subkeys are distinct and the relevant behavior is covered by tests.

Written by the indexing model from the issue text.

Assessment

Domain
cryptography, security
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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